The present invention relates to a new process and apparatus for producing furnace carbon blacks.
Carbon blacks are widely utilized as pigments in ink compositions, paints and the like; as fillers and reinforcing pigments in the compounding and preparation of rubber compositions and plastic compositions, and for a variety of other applications. Carbon blacks are generally characterized on the basis of their properties including, but not limited to, their surface areas, surface chemistry, aggregate sizes and particle sizes. The properties of carbon blacks are analytically determined by tests known to the art.
Carbon blacks are generally produced in a furnace-type reactor by reacting a hydrocarbon feedstock with hot combustion gases to produce combustion products containing particulate carbon black. In the carbon black literature, this reaction between the combustion gases and the hydrocarbon feedstock is generally referred to as pyrolysis.
A variety of methods for producing carbon blacks are generally known. In one type of a carbon black furnace reactor, such as shown in U.S. Pat. No. 3,401,020 to Kester et al., or U.S. Pat. No. 2,785,964 to Pollock, hereinafter xe2x80x9cKesterxe2x80x9d and xe2x80x9cPollockxe2x80x9d respectively, a fuel, preferably hydrocarbonaceous, and an oxidant, preferably air, are injected into a first zone and react to form hot combustion gases. A hydrocarbon feedstock in either gaseous, vapor or liquid form is also injected into the first zone whereupon reaction of the hydrocarbon feedstock commences. The resulting combustion gas mixture, in which the reaction is occurring, then passes into a reaction zone where completion of the carbon black forming reaction occurs.
In another type of carbon black furnace reactor a liquid or gaseous fuel is reacted with-an oxidant, preferably air, in the first zone to form hot combustion gases. These hot combustion gases pass from the first zone, downstream through the reactor, into a reaction zone and beyond. To produce carbon blacks, a hydrocarbonaceous feedstock is injected at one or more points into the path of the hot combustion gas stream. The hydrocarbonaceous feedstock may be liquid, gas or vapor, and may be the same or different than the fuel utilized to form the combustion gas stream. Generally the hydrocarbonaceous feedstock is a hydrocarbon oil or natural gas. The first (or combustion) zone and the reaction zone may be divided by a choke or zone of restricted diameter which is smaller in cross section than the combustion zone or the reaction zone. The feedstock may be injected into the path of the hot combustion gases upstream of, downstream of, and/or in the restricted diameter zone. The hydrocarbon feedstock may be introduced in atomized and/or non-pre atomized form, from within the combustion gas stream and/or from the exterior of the combustion gas stream. Carbon black furnace reactors of this type are generally described in U.S. Reissue Pat. No. 28,974, to Morgan et al., and U.S. Pat. No. 3,922,335, to Jordan et al., the disclosure of each being incorporated herein by reference.
In generally known reactors and processes, the hot combustion gases are at a temperature sufficient to effect the reaction of the hydrocarbonaceous feedstock injected into the combustion gas stream. In one type of reactor, such as disclosed in Kester, feedstock is injected, at one or more points, into the same zone where combustion gases are being formed. In other type reactors or processes, the injection of the feedstock occurs, at one or more points, after the combustion gas stream has been formed. The mixture of feedstock and combustion gases in which the reaction is occurring is hereinafter referred to, throughout the application, as xe2x80x9cthe reaction streamxe2x80x9d. The residence time of the reaction stream in the reaction zone of the reactor is sufficient to allow the formation of desired carbon blacks. In either type of reactor, since the hot combustion gas stream is flowing downstream through the reactor, the reaction occurs as the mixture of feedstock and combustion gases passes through the reaction zone. After carbon blacks having the desired properties are formed, the temperature of the reaction stream is lowered to a temperature such that the reaction is stopped.
U.S. Pat. No. 4,327,069, to Cheng (xe2x80x9cCheng ""069xe2x80x9d), and its divisional, U.S. Pat. No. 4,383,973, to Cheng (xe2x80x9cCheng ""973xe2x80x9d), disclose a furnace and a process for producing carbon black having a low tint residual utilizing two carbon black reactors. xe2x80x9cEach of the carbon black reactors has a precombustion section, a reaction section, hydrocarbon inlet means, and hot combustion gas inlet meansxe2x80x9d. Cheng ""973, Col. 4, 11. 16-19. One of the reactors is a high-structure carbon black reactor, and the other reactor is a low-structure carbon black reactor. Cheng ""973, Abstract. xe2x80x9cA second flow of hot combustion gases formed by the combustion of a second fuel stream and a second oxygen containing stream is established in the second carbon black forming zone. A second stream of hydrocarbon feedstock is introduced into the second carbon black forming zone of the furnace into admixture with the second flow of hot combustion gases established therein as well as with the first carbon black forming mixture coming from the first carbon black forming zone of the furnace.xe2x80x9d Cheng ""973, Col. 2, 11. 19.
I have discovered that it is possible to reduce the amount of fuel utilized to produce carbon black by reacting the reaction stream of a prior carbon black forming process with an oxidant to generate a stream of combustion products that will react with carbon black yielding feedstock to produce carbon black. The generation of this stream of combustion products may be accomplished by introducing any suitable oxidant, which may be any oxygen containing material such as air, oxygen, mixtures of air and oxygen, or other like materials into the reaction stream. The resulting stream of combustion products is reacted with additional carbon black yielding feedstock to produce carbon black. As a result, the amount of fuel utilized for producing carbon black is reduced.
Accordingly, the process of the present invention is a process for producing carbon black comprising:
reacting a reaction stream formed by a prior carbon black forming process with an oxidant and a carbon black yielding feedstock to produce carbon black; and
cooling, separating and recovering the carbon black. Preferably, the process further comprises:
forming the reaction stream by a process comprising reacting a fuel with an oxidant and a carbon black yielding feedstock; and
reacting the reaction stream with oxidant and carbon black yielding feedstock under conditions that reduce the amount of fuel utilized to produce the total amount of carbon black produced by the process. The fuel reduction is observed in the amount of fuel utilized per pound of carbon black produced by the process when compared to the amount of fuel utilized per pound of carbon black to form the reaction stream. More particularly, the amount of fuel utilized, per pound of carbon black, to produce the total amount of carbon black produced by the process, is less than the amount of fuel, per pound of carbon black, utilized to produce a carbon black, of not less than substantially the same CTAB surface area, by the process which formed the reaction stream. If one operates a typical carbon black producing process to produce a carbon black of a given CTAB surface area, and, prior to cooling, separating and recovering the carbon black, reacts the reaction stream with an oxidant and carbon black yielding feedstock, according to the process of the present invention, it is possible and practicable to produce more total carbon black of not less than substantially the same CTAB surface area at a lower specific fuel consumption (BTU/pound of carbon black) than the typical carbon black forming process preceding the reaction between the reaction stream and the oxidant and carbon black yielding feedstock. Preferably, the reduction in the amount of fuel is at least 2%.
As will be understood by those of ordinary skill in the art, the process steps of reacting a reaction stream with an oxidant and a carbon black yielding feedstock to produce carbon black may be repeated, as often as practicable, prior to cooling, separating and recovering the carbon black.
From the Examples described herein, and cited in Tables 4 and 5 below, it is evident to one of ordinary skill in the carbon black art that significant fuel savings have been achieved by the practice of my invention. In the Examples, the reaction stream was generated in a carbon black furnace reactor similar to those described in U.S. Reissue Pat. No. 28,974, to Morgan et al., and U.S. Pat. No. 3,922,335, to Jordan et al. However, the process of the present invention may be performed using any means of forming the reaction stream. For example, the process of the present invention may be performed, and useful fuel savings could be achieved, utilizing a reaction stream formed in the following generally known types of reactors: a typical carbon black furnace reactor of the type described in U.S. Pat. No. 2,641,534; and a set of thermal carbon black reactors appropriately ganged and valved so as to provide a substantially continuous reaction stream.
xe2x80x9cOxidantxe2x80x9d, as used herein, refers to any oxidizing agent suitable for maintaining a fire, such as, for example, air, oxygen and mixtures thereof, with air being the preferred oxidant. The process of the present invention may even gainfully employ air with reduced oxygen content. It is within the context of the present invention to vary the composition of the oxidant, through the introduction of additives.
Oxidant may be introduced into the reaction stream in any manner known to the art. For example, and preferably, the oxidant may be introduced by attaching a conduit to a port through the walls of the reactor. However, oxidant should be introduced in a manner, or the reactor configured in a manner, such that the oxidant is rapidly mixed into the reaction stream. The mixing of the oxidant into the reaction stream may be accomplished by methods which include, but are not limited to, the following methods: introducing the oxidant under sufficient pressure to penetrate the reaction stream; or configuring the reactor to include a recirculation zone to allow the mixing of the oxidant into the reaction stream.
Carbon black-yielding hydrocarbon feedstocks, which are readily volatilizable under the conditions in the reactor, include unsaturated hydrocarbons such as acetylene; olefins such as ethylene, propylene, butylene; aromatics such as benzene, toluene and xylene; certain saturated hydrocarbons; and volatilized hydrocarbons such as kerosenes, naphthalenes, terpenes, ethylene tars, aromatic cycle stocks and the like.
Carbon black yielding feedstock may be introduced into the reaction stream simultaneously with or subsequent to the introduction of the oxidant. The feedstock may be introduced in atomized and/or non-pre atomized form from within the reaction stream, and/or from the exterior of the reaction stream. The time between the introduction of the oxidant, and the introduction of the carbon black yielding feedstock, should allow sufficient time for the mixing of the oxidant and the reaction stream, such that the reaction between the oxidant and the reaction stream generates a stream of combustion products to react the carbon black yielding feedstock.
Preferably, in the process of the present invention, the time between the introduction of the oxidant and the introduction of the carbon black yielding feedstock is less than 30 milliseconds, more preferably less than 10 milliseconds, most preferably less than 5 milliseconds.
Introduction of the oxidant into the reaction stream generates sufficient heat to react the carbon black yielding feedstock. The reaction stream may then be passed into another reaction zone to permit the introduction of additional oxidant and additional carbon black yielding feedstock according to the process of the present invention.
After carbon blacks having the desired properties are formed the temperature of the reaction stream may be lowered, in any manner known to the art, such as by injecting a quenching fluid, through a quench, into the reaction stream. One way of determining when the reaction should be stopped is by sampling the reaction stream and measuring its toluene discoloration level. Toluene discloration is measured by ASTM D1618-83 xe2x80x9cCarbon Black Extractablesxe2x80x94Toluene Discolorationxe2x80x9d. The quench is generally located at the point where the toluene discoloration level of the reaction stream reaches an acceptable level for the desired carbon black product being produced. After the reaction stream has been cooled, the reaction stream may be passed through a bag filter system to separate and collect the carbon black.
An apparatus for carrying out the process of the present invention comprises:
means for reacting a reaction stream formed by a prior carbon black forming process with an oxidant and a carbon black yielding feedstock to produce carbon black; and
means for cooling, separating and recovering the carbon black.
Preferably, the apparatus comprises a plurality of reactor zones in which a reaction stream is formed in a first reaction zone and flows into at least one subsequent reaction zone wherein oxidant and carbon black yielding feedstock are introduced to form carbon black. After the formation of carbon black, the reaction stream is cooled and the carbon black separated and recovered. It is therefore within the contemplation of this invention that the reaction stream may be allowed to flow downstream into additional reaction zones for the introduction of further oxidant and carbon black yielding feedstock.
Other details and advantages of the process and apparatus of the present invention will become apparent from the following more detailed description.